1. Technical Field
The present invention relates to compositions comprising nanoparticles of a metal and/or alloy or nanoparticles comprising a metal or alloy core surrounded by an oxide shell in admixture with platinum particles in a catalyst ink. More particularly, the composition is useful for inks used to make anode and cathode electrodes, which may be used in electrochemical devices, such as direct methanol fuel cells (DMFCs), direct formic acid fuel cells (FAFCs), hydrogen fuel cells (H2-PEMFCs), and alkaline fuel cells (AFCs).
2. Related Art
Platinum is highly catalytic for hydrocarbon or hydrogen oxidation and oxygen reduction in gas diffusion electrodes for a variety of fuel cells. However, this noble metal is a rapidly depleting non-renewable resource and is consequently expensive. Current price for bulk platinum black is $75.00/gram. The associated cost of a platinum deposited electrode, typically loaded anywhere from 2-8 mg/cm2, is widely considered to be a hurdle to widespread commercialization. With the gaining demand for alternative energy sources by consumers, efficient catalysts, especially at practical operating temperature (room temperature to 60° C.) must be discovered to alleviate the demand and expense of platinum. Based on this, considerable effort is being dedicated to find an alternative catalyst which can match or exceed platinum's electrical performance. Method of synthesis of metal nanoparticles has been previously described in U.S. patent application Ser. No. 10/840,409, as well as their use in air cathodes for batteries in U.S. patent application Ser. No. 10/983,993 both of which applications have the same assignee as the present application. The disclosures of these applications are incorporated herein by reference.